Na2CaP2O7:Cr3+ phosphor toward broadband emission

Global research interest in near-infrared phosphors has increased due to their potential applications in night vision, agriculture, and bio-applications. This work utilized a high-temperature solid-state technique to synthesize a broadband near-infrared phosphor Na2Ca1-xP2O7: xCr3+ (x = 0.01–0.10). The phosphor exhibits a broadband emission with a peak centered at 850 nm and a full width at half maximum (FWHM) of 176 nm when excited at 442 nm. The crystal field parameters, optical characteristics, and luminescence decay curves of the Na2Ca1-xP2O7: xCr3+ (x = 0.01–0.10) phosphors are discussed in detail. The sample shows the strongest emission when the Cr3+ doping concentration is 0.05. The critical energy transfer distance has been calculated, and the interaction mechanism in Na2Ca1-xP2O7: xCr3+ (x = 0.01–0.10) is verified to be a dipole-dipole interaction. The doping concentration of Cr3+ is effectively enhanced by isolated doping sites, which offers a new perspective on the design of NIR-emitting phosphors with high doping contents. •The NIR-emitting Na2CaP2O7:Cr3+ phosphors were synthesized by a high-temperature solid-state technique.•Na2CaP2O7:Cr3+ phosphors, with an FWHM 176 nm, achieve broadband NIR emissions ranging from NIR-I to NIR-II window.•The absorption efficiency of Na2CaP2O7:Cr3+ is 28 %.